The present invention relates to a symbol synchronizing device, and more particularly to an improvement technology which effectively enables symbol synchronization establishment and synchronization holding for an arbitrary spread code sequence.
As an approach for establishing symbol synchronization between a transmitter and a receiver in a digital radio communication using a spread spectrum communication system, a method for enhancing a symbol sequence for synchronization by performing an in-phase addition of receive signals and detecting correlation after improving the signal to noise ratio (SNR) of the receive signals is disclosed in Japanese Patent Application Laid-Open No. 2003-333011. According to this method, symbols for synchronization can be easily detected even if correlation detection is difficult due to inter-symbol interference and noise.
With this method, however, phase information is detected by correlation detection, so the auto-correlation characteristics of the spread code sequence of symbols for synchronization influence the symbol synchronization characteristics. Therefore, if the synchronization method based on correlation detection is used for a system which uses a plurality of spread codes for a data symbol sequence, then symbol synchronization establishment and synchronization holding when a data symbol sequence is being received becomes difficult.